Question

When solid ammonium nitrate dissolves in water, the solution becomes cold. This is the basis for an "instant ice pack". When 3.21 g of solid NH₄NO₃ dissolves in 50.0 g of water at 24.9 °C in a calorimeter, the temperature decreases to 20.3 °C. Calculate the value of q for this reaction and explain the meaning of its arithmetic sign rage

a. q would be (+) and the reaction is endothermic.
b. q would be (+) and the reaction is exothermic.
c. q would be (-) and the reaction is endothermic.
d. q would be (-) and the reaction is exothermic.

Answer 1

The reaction where ammonium nitrate dissolves in water is endothermic, as the temperature of the water decreases. The value of q would be negative, indicating that heat is absorbed, thus option c is the correct answer.

Step-by-step explanation:

When ammonium nitrate (NH₄NO₃) dissolves in water, the process is endothermic, meaning that heat is absorbed from the surroundings.

The decrease in temperature upon dissolution supports this, as indicated by the temperature drop from 24.9 °C to 20.3 °C in the scenario provided. To calculate the value of q for the reaction, we'd use the formula q = m × Cs × ΔT, where m is the mass of the water, (Cs) specific heat capacity of water (4.184 J/g°C), and ΔT - change in temperature.

The change in temperature (ΔT) is negative because the final temperature is lower than the initial temperature, which means heat was absorbed by the solution, making q negative as well. Hence, the correct answer is: c. q would be (-) and the reaction is endothermic.